This invention relates to frames that are used to mount and to provide tension for flexible fabrics, such as artists' canvases, silk screen, and the like, and, more particularly, to frames that that can be adjusted for varying the tension in such fabrics.
In the past most artists' canvases or other fabrics have been mounted on square or rectangular wooden frames the corners of which were mitered and frequently exhibited dove-tail or other types of interlocking features. An artists' canvas is normally attached to the frame with tacks or staples and tensioned by hand to remove wrinkles as it is applied. If additional tension is required at the time of assembly or at a later time it is usually applied by inserting wedges in each corner joint and driving them in with a mallet to spread the joint thereby adding tension to the affixed fabric.
Stretcher frames of this type have numerous disadvantages. The insertion of wedges to adjust tension is a tedious process that subjects a mounted canvas, particularly an old canvas that may have become weak or brittle, to risk of damage. Wooden frames dry, shrink and crack with age tending to loosen the canvas and cause previously inserted tensioning wedges to fall out of the joints. These problems caused by the aging of the wooden frames will become more acute in the future as forests are destroyed and the shortage of quality woods forces the use of less stable wood in frames. A further disadvantage of past framing practice is that the interlocking joinery used in the corners of the frames, due to its complexity and precision, must usually be done by a frame manufacturer rather than at a retail shop most of which have tools no more complex than a miter saw. Thus retailers are required to keep in stock a complete range of sizes of stretcher bars that may be needed rather than stocking bulk material that can easily be cut to the lengths desired.
Stretcher bars should ideally be constructed so that the frame surfaces, which face the painting surface of the fabric, are angled inward so that only the outer edge of each frame member, not the entire surface, comes into contact with the canvas. This ideal mounting can be accomplished by using more complex joinery and/or brackets in each corner of the frame to tilt each frame member so that only the edge of the member contacts the front surface of the fabric or by the expensive milling away a portion of the front surface of each the frame members leaving only a bead of wood along the outer edge of each frame to support the fabric.
These problems are addressed by the present invention, and a fabric stretching system is provided that can be assembled from bulk materials that can be sized for individual frames using conventional equipment in frame shops.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.